Manufacture of monomethyl-paraaminophenol and its sulphate



Patented Dec. 7, 1937 V r MANUFACTURE OF MONOMETHYL-PARA- AMINOPHENOL AND ITS SULPHATE Simon Norman, Providence, R. 1., assignorto Industrial Dyestufi Company, East Providence, R. 1., a corporation of Rhode Island Nb Drawing. Application July 30, 1935, Serial No. 33,915

12 Claims. (o1.26o 12s This invention. relates to improvements in' the, manufacture of N- methyl-para-aminophenol, sulphate, and more particularlyto improvements in the process of converting parahydroxy-phen ylglycine into N-moncmethylpara-aminophenol, which, in turn, is converted into the sulphate.

It is, well known that by heating para-hydroxyphenylglycine in the presence of a, large excess of phenol to about 170C decomposition of the glycine occurs with the formation of N-me'thylparaaminophenol. 1 It has recently been proposed to employ anj excess of cresylic acid or other protective media, such as xylenols, thymol, carvacrol, and benzaldehyde, in place oiphenol, at

temperatures ranging from 165 C. to 185 C. 'The proportions of these media employed are,

generally from ten to twelve times the weight of the glycine. v It has been extremely .difiicult to findmedia which are not required in such large amounts in order to complete the decomposition of the glycine in a reasonable time and which do not resinify when heated for long periods in contact-with methylated aminophenol, especially when used in large scale production in the factory. It has also been difiicult to prevent decomposition of N-methyl-para-aminophenol formed during the heat treatment. Decomposition of the N-methylpara-aminophenol and resihification seriously afiect the yield of the, finished N-me'thyl-paraaminophenol 'sulphate, 'as Well as the recovery of themedia. V 1= An object of the present invention is,therefore, to provide a process in which the aforesaid difficulties, particularly that of preventing resinification and that of preventing decomposition of the final product, are overcome.

Another object is to provide a highly efiicient process in which para-hydroxy-phenylglycine is decomposed under controlled conditions in a mediumof such nature as to cause a rupture of the glycine grouping at a relatively low ternperature and bring about the completion of the reaction in arelatively short time.

v A further object is to provide a relatively inexpensive process by which to carry on the above reaction, and Which process permits of practically complete recovery of the final product and of the media in which the reaction is carried out.

The media which are employed'in the present process have been found to be even more satisfactory than the products of the hydrogenation of phenols, cresols', and their homologs, and they consist of a whole series of aliphatic ketones.

I have found that any aliphatic ketone, pref,-

.erably those containing one methyl or ethyl group attached to the 0:0 linkage and boiling at 145 C., or over, or mixtures of the same, hav-:

ing a. resultant boiling range above 145. C., will decompose para-hydroxy-phenylglycine satisfactorily and give the resultant compound, monomethylparaaminophenol.

It has been found that the reactions herein disclosed require much lesser amount-sic efiect the decomposition than any of the compounds mentioned in the prior art, and still allow a very small'amount of by-products andimpurities to form.

The following examples serve to illustrate the present invention:

ErcampleL-Jnto a suitable apparatus, charge 30 parts (by weight) of para-hydroxy-phenylglycine and parts (by weight) of methyl-namylketone. The mass is now stirred and heated to attain a temperature of about 148 C. The temperature is now maintained at this point for a period of about one hour and the whole stirred until inspection of a sample shows a complete solution has been obtained, following which it can be concluded that decomposition is at an end. The massin the apparatus is now cooled exter nally to about 25 C. whereupon it is diluted by ethyl alcohol and the whole well mixed. The diluted mass is now treated with the stoichio metric amount of concentrated sulphuric acid, which-"causes the sulphate of N-monomethylpara-aminophenol to separate from the solution.

monomethyl-para-aminophenolsulphate is ob-- .tained in excellent yield 'and high purity. It

will be noted that, in this example, 2 parts of methyl-n-amylketone convert with very satisthe addition of about parts (by weight) of 7 After stirring the mass for a suitable period of I I time, it is filtered ofi and washed with alcohol until the mother liquor has been removed. The N- media, at least 5 parts and sometimes 10 parts of solvent are required to finish the decomposi tion in a time short enough, and still allow a very is treated with alcohol and sulphuric acid, as in Example 1.

Example 3.1 part (by Weight) of para-hydroxy-phenylglycine is mixed with 5 parts (by weight) of methyl-n-nonylketone. The mass is heated for about 20 minutes, at 160 C.-180 0., when all the glycine is found to be converted. The resulting product is treated with alcohol and sulphuric acid, as above.

Example 4.--1 part (by weight) of para-hydroxy-phenylglycine is mixed with 5 parts (by weight) of methyl-butylketone and 5 parts (by weight) of methyl-hexylketone. The temperature of the mass is brought to C. C., and conversion occurs in about 20 minutes. Theresulting product is then treated as in the previous examples.

Example 5.-1 part (by weight) of para-hydroxy-phenylglycine is mixed with 5 parts (by weight) of methyl-propylketone and 5 parts by weight) of methyl-n-nonylketone. The temperature of themixture is brought to 150 C. C., and it is converted in about 20 minutes. The process is then finished by treating the mass as above. It will be noted, in this example, that a mixture of a low boiling ketone and a high boiling ketone, to give a boiling range of from 150 C.- 160 (3., gave a satisfactory result. Consequently, where the boiling point of the pure aliphatic ketone is below 145 C., the addition of enough higher boiling ketone will give a resultant boiling point in the decomposition temperature range, and still give a satisfactory result.

Example 6.-1 part (by weight) of para-hydroxy-phenylglycine is mixed with 5 parts (by weight) of ethyl-undecylketone. The whole is heated to 180 C.200 C., for a period of 15 minutes, with the resulting formation of monomethyl-para-aminophenol base. The mass is then treated as in the previous examples.

What I claim is:

1. A process of manufacturing monomethyh para-aminophenol, which process comprises decomposing para-hydroxyphenylglycine to monomethyl-para-aminophenol in a reaction medium containing essentially a straight chain aliphatic ketone having a boiling point above 145 C.

2. A process of manufacturing monomethylpara-aminophenol, which process comprises decomprising para-hydroxy-phenylglycine to monoethyl-para-aminophenol in a reaction medium containing essentially methyl-n-amylketone.

3. In the process set forth in claim 2, the steps which consist in mixing 1 part, by weight, of para-hydroxy-phenylglycine with 2 parts, by weight, of methyl-n-amylketone, heating the mixture for one hour at a temperature of about 148 C., cooling the mass to about 25 C. and diluting it with about '7 parts, by weight, of ethyl alcohol, neutralizing the mass with concentrated sulphuric acid to produce the sulphate of monomethyl-para-aminophenol, and then filtering off and Washing the precipitate with alcohol. I

4. A process of manufacturing monomethylpara-aminophenol, which process comprises decomposing para-hydroxy-phenylglycine to monomethyl-para-aminophenol in a reaction medium containing essentially methyl-n-hexylketone.

5. In the process set forth in claim 4, the steps which consist in mixing 1 part, by weight, of parahydroxy-phenylglycine with 5 parts, by weight, of methylm-hexylketone, heating the mixture for 25 minutes to a temperature of 160 C.- 'C., treating the resulting product with alcohol and then with concentrated sulphuric acid to produce the sulphate of monomethyl-paraaminophenol.

6. A process of manufacturing monomethylpara-aminophenol, which comprises decomposing para hydroxy phenylglycine to monomethylpara-aminophenol in a medium containing essentially methyl-n-nonylketone.

7. In the process set forth in claim 6, the steps which consist in mixing 1 part, by weight, of para-hydroxy-phenylglycine with 5 parts, by weight, of methyl-n-nonylketone, heating the mixture to 160 C.- C., for a period of about 20 minutes, diluting the resulting mass with alco- 1101, and adding sufficient sulphuric acid to convert the 'monomethyl-paraaminophenol base into monomethyl-para-aminophenol sulphate.

8. A process of manufacturing monomethylpara-aminophenol, which process comprises decomposing para-hydroxyphenylglycine to monomethyl-para-aminophenol in a reaction medium containing essentially an aliphatic ketone containing one methyl group attached to the C=O linkage and having a boiling point of at least 145 C.

9. A process of the character described, comprising decomposing para-hydroxy-phenylglycine to monomethyl-para aminophenol in a reaction medium containing essentially a straight chain aliphatic ketone having a boiling point of at least 145 C., and stirring the reaction mixture with a solution containing an amount of sulphuric acid sufficient to convert the monomethylpara-aminophenol base into monomethyl-paraaminophenol sulphate.

10. A process of the character described, com-.

prising decomposing para-hydroxy-phenylglycine to monomethyl-para-aminophenol in a reaction medium containing essentially a straight chain aliphatic ketone having a boiling point of at least 145 C., diluting the resulting mass with alcohol, and adding suflicient sulphuric acid to convert the monomethyl-para-aminophenol base into monomethyl-para-aminophenol. sulphate.

11. In the process set forth in claim 10, the additional steps of stirring the resulting mass for 'a period of about twenty minutes, filtering off and then washing 01f with alcohol until the mother liquor has been removed.

12. A process of manufacturing monomethylpara-aminophenol, which process comprises de composing para-hydroxy-phenylglycine to monomethyl-para-aminophenol by means of heat in a protecting medium comprising essentially a straight chain aliphatic ketone having a boiling point of at least 145 C.

SIMON NORMAN.

CERTIFICATE OF CORRECTION, Patent No. 2,101,7L9. December "T, 1957.

' SIMON NORMAN.

It is hereby certified-that error appears in the printed specification of the above numbered patent requiring correction as follows:' Page 2, first column, line 50-51, claim 2, for "mono-ethyl-para -aminophenol" read monomethyl-para-aminophenol; and that the said Letters Patent. should be read with this correction therein that the same may conform to the record of the case in the Patent Office. I

signed and sealed this 5th day of March, A, D. 19m).

Henry Van Arsdale, (seal) I Acting Commissioner of Patents. 

